Aircraft brake and method with electromechanical actuator modules

ABSTRACT

An electrically actuated aircraft brake and method characterized by the use actuator modules which can be easily and quickly replaced as a unit. Quick and easy replacement of the actuator modules can be effected without disassembly of the overall brake and wheel assembly. Accordingly, brake manufacturing, repair costs, overhaul, parts stocking and maintenance costs and requirements are minimized and/or greatly simplified compared to integrated brake designs used in the prior art. Also, a malfunctioning actuator module on an aircraft can be replaced and preferably quickly enough to allow the aircraft to remain in scheduled service and/or with a minimum of downtime.

FIELD OF THE INVENTION

The invention herein described relates generally to brakes and methods,ore particularly to brakes and methods using electromechanicalactuators, and still more particularly to electrically actuated aircraftbrakes and methods.

BACKGROUND OF THE INVENTION

Aircraft wheel and brakes heretofore have included a non-rotatable wheelsupport, a wheel rotatably mounted to the wheel support, and a brakedisk stack having alternating rotor and stator disks mounted withrespect to the wheel support and wheel for relative axial movement. Eachrotor disk is coupled to the wheel for rotation therewith and eachstator disk is coupled to the wheel support against rotation. A backplate is located at the rear end of the disk pack and a brake head islocated at the front end. The brake head may house a plurality ofactuator rams that extend to compress the brake disk stack against theback plate. Torque is taken out by the stator disks through a statictorque tube or the like.

Electrically actuated aircraft brakes of various configurations areknown, as exemplified by U.S. Pat. Nos. 4,381,049, 4,432,440, 4,542,809and 4,567,967. The brakes shown in these patents include electric motorswhich respond to an electrical control signal to effect rotation of aring gear member which interacts through a plurality of balls to drive alinearly movable ram member into contacting engagement with a brake diskstack to effect compression thereof and braking of a wheel.

In U.S. Pat. No. 4,596,316, another configuration of an electricallyactuated brake uses a roller screw drive wherein a ring gear memberinteracts through a plurality of roller screws to drive a ram memberinto engagement with a brake pressure plate to effect compression of thebrake disk stack for braking action. A plurality of electric motors andtheir associated pinions drive a ring gear into rotation and theplurality of roller screws effect linear axial movement of the rammember.

In U.S. Pat. No. 4,865,162, a further electrically actuated aircraftbrake employs a roller screw drive mechanism driven by an electrictorque motor through a gear drive associated with either the screw orthe nut of the roller screw drive mechanism. Rotation of the gear driveby the torque motor moves the other one of the screw or nut into axialengagement with a brake disk stack to compress the stack for braking. Aplurality of the roller screw drive mechanisms and respective geardrives and torque motors are assembled in a brake head in a balancedarrangement about the axis of the wheel to apply and release a brakepressure force on the brake disk stack in response to an electricalcontrol signal to the torque motors.

The repair or maintenance of these presently known brakes includingtorque motor driven rams heretofore has required significant disassemblyof the brake. The complex integrated nature of prior art designsnormally require substantial teardown of the assembly for maintenance,repair and/or overhaul of the assembly even if minor repair or onlyreplacement of a single faulty component is required. Associated withextensive teardown is a lengthy reassembly and retest procedure toverify flight worthiness. Also, a highly integrated design and assemblywith complex machining and assembly procedures is costly to process andmanufacture. Distribution and parts stocking of individual components ofsuch an assembly is similarly complex and inefficient as can beappreciated by those knowledgeable in this area. Consequently, anaircraft, for example a commercial passenger aircraft, would most likelyhave to be taken out of scheduled service until a faulty actuator couldbe serviced. This results in lost revenue for the airline, schedulingadjustments, considerable inconvenience for customers, etc.

SUMMARY OF THE INVENTION

The present invention provides a brake and method characterized by theuse actuator modules each of which can be easily and quickly replaced asa unit. This enables quick and easy replacement of the actuator modulespreferably without requiring disassembly of the overall brake and wheelassembly. Also, it is conceivable that a malfunctioning actuator modulecould be replaced on an aircraft and tested with a minimum of equipmentpreferably quickly enough to allow the aircraft to remain in scheduledservice and/or with a minimum of downtime. In addition, periodicmaintenance of the brake can be done quicker and more efficiently byreplacing the actuator modules with reconditioned and/or new actuatormodules.

Accordingly, a preferred embodiment of a brake according to the presentinvention comprises a brake disk stack, a brake head, and at least oneactuator module mounted to the brake head. The actuator module includesa module housing, a reciprocating ram and a motive device operativelyconnected to the reciprocating ram for selectively moving thereciprocating ram into and out of forceful engagement with the brakedisk stack for applying and releasing braking force. In accordance withthe invention, the actuator module is removable as a is unit from oneside of the brake head.

Further in accordance with a preferred embodiment of the invention, theactuator module is removable from the brake head from the side thereofopposite the brake disk stack and the ram is guided in the modulehousing for movement toward and away from the brake disk stack. The ramincludes a ram nut, and the motive device preferably includes anelectric motor drivingly connected to a lead screw (preferably a ballscrew although other type of screw drives and the like are contemplated)in threaded engagement with the ram nut whereupon rotation of the leadscrew effects linear movement of the nut toward and away from the brakedisk stack. The ram nut preferably is guided in the module housing formovement toward and away from the brake disk stack. To this end, themodule housing includes a guideway for guiding the ram nut, and theguideway and ram nut respectively have polygonal cross-sections definedby plural outer side surfaces which rotationally interfere with oneanother to restrain rotation of the ram nut relative to the housing.

In a preferred application, the brake is used in combination with anaircraft wheel assembly.

According to another aspect of the invention, there is provided a methodfor servicing the aforesaid brake. The method comprises the steps ofidentifying a brake module to be replaced, and removing and replacingthe identified brake module with another brake module withoutdisassembly of the brake disk stack. Preferably, when the brake is partof a wheel and brake assembly, the removing and replacing step includesremoving and replacing the identified brake module without removal ofthe wheel from the wheel and brake assembly.

The foregoing and other features of the invention are hereinafter fullydescribed and particularly pointed out in the claims, the followingdescription and the annexed drawings setting forth in detail one or moreillustrative embodiments of the invention, such being indicative,however, of but one or a few of the various ways in which the principlesof the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an aircraft brake including pluralactuator modules mounted to a brake head according to the presentinvention.

FIG. 2 is an axial end view of the actuator modules and brake headlooking from the line 2--2 of FIG. 1, with one of the modules removed.

FIG. 3 is cross-sectional view taken along the line 3--3 of FIG. 2,showing one actuator module mounted to the brake head.

FIG. 4 is a cross-sectional view taken along the line 4--4 of FIG. 3.

FIG. 5 is a fragmentary cross-sectional view of a modified aircraftbrake according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Because the invention was conceived and developed for use in an aircraftbraking system, it will be herein described chiefly in this context.However, the principles of the invention in their broader aspects can beadapted to other types of braking systems, such as in train brakesystems.

Referring now in detail to the drawings and initially to FIG. 1, a wheeland brake according to the present invention is generally indicated at10. The assembly 10 generally comprises a brake 11 and an aircraft wheel12 which is supported for rotation by bearings 13 and 14 on an axle 15.The axle 15 forms a wheel mount and is attached to the end of anaircraft landing gear strut (not shown) or a truck attached to the endof a landing gear strut.

The brake 11 includes a brake head or housing 20 which is attached bybolt fasteners 21 to a torque tube 22 which in turn is attached by boltfasteners 23 to a torque take-out flange on the axle 15. Although theinvention is being illustrated in the context of a flange mounted typeof brake, the principles of the invention may be applied to other typesof brakes such as to a torque lug type of brake as will be appreciatedby those skilled in the art. The illustrated brake head is a generallyplanar disk-like plate member having a bolt circle surrounding a centralopening as best shown in FIGS. 1 and 2.

The torque tube 22 is surrounded by stationary brake elements and rotarybrake elements that are interleaved. The stationary and rotary brakeelements are in the form of stator disks 25 and rotor disks 26, and theinterleaved arrangement thereof is commonly referred to as a brake diskstack, the same being designated by reference numeral 27. The statordisks 25 are splined to the torque tube and the rotor disks 26 aresplined to the wheel 12 interiorly of the wheel's rim. As isconventional, the splined connection may be effected by a plurality ofspline or drive keys that are spaced around the circumference of therim/torque tube to permit axial movement of the rotor/stator disks whilebeing held to the wheel/torque tube against relative rotation.

The disk stack 27 is located between a back pressure member 31 and thebrake head 20. The back pressure member 31 is formed by a radial flangeat the outer end of the torque tube 22. The radial flange carriesthereon a plurality of circumferentially spaced torque pucks 33 engagedwith the last brake disk 34 at the rear end of the disk stack 27. Thetorque pucks 33 may be attached in a known manner to the radial flange31 by several torque pucks which have the stems thereof loosely fittedin holes in the radial flange to permit some swiveling movement thereof.The torque pucks in the illustrated embodiment secure the last brakedisk 34 against rotation relative to the torque tube. In a modifiedarrangement, the radial flange could be configured to engage directlythe disk pack, and still other arrangements could be used.

Pressure is applied to the front end of the disk stack 27 by one or moredisk engaging members which in the illustrated embodiment are theinboard ends of one or more actuator rams 35. The actuator rams 35 areincluded in respective actuator modules 36 mounted to the brake head 20by removable bolt fasteners 37 or other suitable means enabling quickand easy attachment and detachment of the actuator modules to and fromthe brake head. As shown in FIG. 2, a plurality of the actuator modules36 are mounted in a circular arrangement around the rotational axis ofthe wheel, preferably with the actuator rams circumferentially equallyspaced apart. The actuator modules each have extending therefrom a cable39 (only two shown) for effecting electrical connection to a brakecontroller (not shown). The controller may include a correspondingnumber of independent servo amplifiers, a microprocessor with associatedperipherals, and data input/output (I/O) circuitry. Details of thecontroller are not being described herein as the invention does notreside in the type of controller or other circuitry used to controloperation of the actuator modules.

Preferably, the modules are identical and interchangeable, and arepresentative one of the actuator modules is shown somewhatschematically in FIG. 3. Each actuator module 36 preferably includes anelectric motor 50, a gear train 51, and a ball screw assembly 52. Themotor 50, gearing 51 and ball screw assembly are all carried in a modulehousing 53. The housing 53 may be composed of one or more housingmembers. In the illustrated embodiment, the housing is primarilycomposed of an outer housing member or casing 54 and an inner housingmember 55. The outer housing member 54 has a dome shape central portion56 surrounded by a mounting flange 57. The mounting flange 57 includesplural holes for the removable bolt fasteners 37 used to removablysecure the housing, and thus the actuator module, to the outboard side58 of the brake head 20. The inner housing member 55 is secured to theouter housing member 54 and substantially closes the interior space ofthe housing and/or maintains the various components of the moduleassembled together as a unit. Such securement may be effected by anysuitable means, such as by the illustrated snap ring 49, for example.

The electric motor 50 may be a DC brushless servo motor. The brushlessDC servo motor 50 may contain, in addition to its motor components, anintegral friction type, electrically actuated brake, and a resolver formotor rotor commutation and angular velocity sensing. The resolver maybe used to provide motor position feedback and velocity information. Thebrake may be a power-on type or a power-off type, as desired for aparticular application. The specific motor selection will be dependenton the requirements for a given braking application.

The gearing 51 includes a pinion 59 on the drive shaft of the electricmotor 50, a transfer gear 60 and a screw gear 61 formed integrally withthe ball screw 62 of the ball screw assembly 52 (although referenceherein is made to certain structures as being integral as is preferred,it should be understood such structures alternatively may be composed ofdiscrete components joined together to form a functionally equivalentstructure). The transfer gear is journalled by bearings between theouter and inner housing members and is in mesh with the pinion and thescrew gear 61. The transfer gear may be realized by a plurality of gearsthat mesh to transmit torque and provide the desired gear ratio from thepinion 59 to the screw gear 61.

The ball screw assembly 52 is comprised of the ball screw 62 with theintegral gear 61, a hexagonal ball nut 63 that translates rotary motionto linear motion of the ball nut, and a ram pad 64 that attaches to theend of the ball nut and provides an insulating interface with the brakedisk stack 27 (FIG. 1). The ball screw and ball nut may be of a knownconfiguration and thus the respective spiral grooves thereof andassociated balls have not been illustrated as the same would beimmediately evident to one skilled in the art. Also, other rotary tolinear motion conversion devices may by employed, if desired, with thelinear moving member coinciding with the ball nut and functioning as theactuator ram. The ball nut (also herein referred to as a ram or ram nut)is free to translate along the axis of the ball screw upon rotation ofthe ball screw, but not to rotate, as the ball nut is guided by a bore65 in a nut slider 66. In the illustrated embodiment, the nut slider 66is formed integrally with the inner housing member 55.

As best seen in FIG. 4, the bore or guideway 65 and the ball nut 63respectively have, in the illustrated preferred embodiment,corresponding polygonal cross-sections defined by plural inner/outerside surfaces (commonly indicated by reference numeral 67) whichrotationally interfere with one another to restrain rotation of the ramnut relative to the inner housing 55. As is preferred and illustrated,one or more of the side surfaces, most preferably all of the sidesurfaces, are planar and form regular polyhedrons providing a closesliding fit between the ball nut and guideway. It will be appreciated,however, that other configurations may be used although less preferred.For example, the number of sides may be varied from the illustratedsix-sided polygons (hexagons), as may be desired for a particularapplication. The six-sided polyhedral configuration provides desiredsliding and anti-rotational characteristics.

Preferably, a lubricant, particularly a suitable grease, is used tolubricate that relatively sliding surfaces 67 of the ball nut 63 andguideway 65. It has been found that the grease and close clearancebetween the ball nut and guideway prevent entry of any appreciableamount of dirt or other foreign material at the sliding surfacesinterface so as to prevent any significant degradation of performance.However, if desired, a suitable seal, such as a wiper seal, bellowsseal, rolling diaphragm seal, etc. could be employed to seal againstpassage of dirt or other undesirable materials between the slidingsurfaces. An exemplary grease for the ball screw and ram nut assembly isMIL-G-81322 and an exemplary grease for the gear train is MIL-G-81827.

When the actuator module 36 is assembled to the brake head as shown inFIG. 3, the nut slider 66 will extend through an opening 68 in the brakehead 20, with the ram pad 64 disposed on the inboard side of the brakehead. Similarly, the motor 50 will pass through an opening 69 (or asingle opening in the brake head including the areas of the openings 68and 69), as needed to accommodate the length of the motor. It is notedthat both the motor 50 and the ram slider 66 and ram 35 will pass freelythrough the respective opening 69 and 68 from the outboard side of thebrake head, i.e., the portions of these components that extend beyondthe outboard surface 58 of the brake head have a cross-section smallerthan that of the openings through in the brake head through which theypass. Accordingly, the actuator module 36 can be assembled to the brakehead from the outboard side thereof and no access to the inboard side ofthe brake head is required to enable assembly or disassembly of theactuator module from the brake head.

An alternate arrangement embodies a larger diameter ram pad 64 (sizedfor a particular braking requirement) which exceeds the diameter ofopening 68. In this embodiment, the ram pad can removably attached tothe end of the ram for easy removal, such as with a quick disconnectdevice and more particularly a spring loaded locking device as isconventional in the art. The known spring loaded device enables removalof the ram pad without the need to remove the brake head 20 form thebrake, to effect diassembly and reassembly of the module 36 with thebrake head 20.

It also is noted that for some applications the motor may be dimensionedor positioned other than as shown, such that the motor may not passcompletely through the brake head or even partially into the brake head.In one arrangement for example, the motor may extend only into a hole inthe brake head that only opens to the outboard side of the brake headand thus is closed at its other end. Also, it the brake envelopepermits, the motor could be located completely outwardly of the brakehead and may be otherwise oriented, such as with its axis extendingperpendicular to the movement axis of the actuator ram.

As shown in FIG. 3, the ball screw 62 is supported in the module housingby three bearings, a radial bearing 70 and a thrust roller bearing 71 atthe outboard end of the ball screw and a radial ball bearing 72 at alocation intermediate the nut-engaging threaded portion of the ballscrew and the integral gear 61. The radial bearing 72 is supported inthe inner housing member 55. The outer housing member 54 locates theradial and thrust bearings and provides mechanical thrust support forthe ball screw. As further shown in FIG. 3, the transfer gear 60 isjournalled between the inner and outer housing members.

Although not shown, the ram nut may have associated therewith an outputram position sensor which provides for actuator position feedback. Forexample, the ball nut 63 (actuator ram 35) may be mechanically connectedto an LVDT position sensor by a bracket. The LVDT armature may beadjustably attached to the bracket (or the sensor body to the modulehousing) by suitable means that provides for LVDT setting and positioncalibration. Other types of position sensors/transducers may be used asdesired for a particular application.

Although it will be immediately evident to those skilled in the art, thepurpose of the brake actuator(s) is to impress a clamping force on astack of brake disk elements. The electromechanical (EM) actuatorsoperate simultaneously to produce a clamping force between a brakereaction or back pressure member 31 and the actuator output rams 35. Thesize and number of actuators may be varied to provide the total brakeclamping force required. The actuators may be operated in a controlleddisplacement mode such that the clamping force is proportional to theposition of the rams. That is, the position of the rams, as opposed tomotor current, preferably is used to obtain desired braking load. It isnoted, however, that brake force control may be carried out in a currentmode.

In the brake shown in FIG. 3, the ram slider 66 is an integral part ofthe module housing, i.e. it is carried by module housing for removalfrom the brake head 20 as a unit along with the other components of theactuator module 36. In an alternative embodiment illustrated in FIG. 5(wherein like parts are identified by the same but primed referencenumerals), the ram slider may instead be formed as an integral part ofthe brake head 20' (that is, the guideway 65' is formed in the brakehead, for example, directly or by a liner fixed in the brake head).Thus, in this embodiment the ram slider is not removable as part of theactuator module 36'. Notwithstanding, the actuator module 36' will stillbe removable as a unit from the outboard side of the brake head 20'. Theinsulator pad 64' on the end of the ram may have a cross-sectional sizeand shape that will allow it to pass through the hole (guideway) in thebrake head, or as previously described the ram pad may be attached tothe ram nut by a quick connect/disconnect device, such as a springdetent device, to enable quick removal of the ram pad from the ram nutand thus enable removal of the actuator module without having to removethe brake head from the brake.

In view of the foregoing, it will now be appreciated that there isprovided a brake assembly that enables easy and quick replacement of amalfunctioning electromechanical actuator. No longer must a brake besubstantially dissembled to repair a malfunctioning actuator or otheractuator identified for repair and/or replacement. Instead, amalfunctioning actuator module 36 (or all of the actuator modules if themalfunctioning module can not be determined) can be removed from thebrake head 20 simply by removing the fasteners 37 and withdrawing themodule from the outboard side of the brake head. This can beaccomplished without having to disassemble the brake disk stack and evenwith the wheel in place on the axle, as access usually can be gained inmost wheel and brake assemblies to the outboard side of the brake head.To facilitate the easy removal and replacement of the actuator modules,the electrical cable 39 (FIG. 2) associated with each module preferablyis equipped with a quick connect/disconnect coupling.

Although the invention has been shown and described with respect to acertain preferred embodiment or embodiments, it is obvious thatequivalent alterations and modifications will occur to others skilled inthe art upon the reading and understanding of this specification and theannexed drawings. In particular regard to the various functionsperformed by the above described integers (components, assemblies,devices, compositions, etc.), the terms (including a reference to a"means") used to describe such integers are intended to correspond,unless otherwise indicated, to any integer which performs the specifiedfunction of the described integer (i.e., that is functionallyequivalent), even though not structurally equivalent to the disclosedstructure which performs the function in the herein illustratedexemplary embodiment or embodiments of the invention. In addition, whilea particular feature of the invention may have been described above withrespect to only one of several illustrated embodiments, such feature maybe combined with one or more other features of the other embodiments, asmay be desired and advantageous for any given or particular application.

In addition, the invention is considered to reside in all workablecombinations of features herein disclosed, whether initially claimed incombination or not and whether or not disclosed in the same embodiment.

What is claimed is:
 1. A brake comprising a brake disk stack, a brakehead, and at least one actuator module mounted to the brake head, theactuator module including a module housing, a reciprocating ram and amotive device operatively connected to the reciprocating ram forselectively moving the reciprocating ram into and out of forcefulengagement with the brake disk stack for applying and releasing brakingforce, and wherein the actuator module is removable as a unit from oneside of the brake head.
 2. A brake as set forth in claim 1, wherein theactuator module is removable from the brake head from the side thereofopposite the brake disk stack.
 3. A brake as set forth in claim 1,wherein the ram is guided in the module housing for movement toward andaway from the brake disk stack.
 4. A brake as set forth in claim 1,wherein the ram is guided in the brake head for movement toward and awayfrom the brake disk stack.
 5. A brake as set forth in claim 1, whereinthe ram includes a ram nut, and the motive device includes an electricmotor drivingly connected to a lead screw in threaded engagement withthe ram nut whereupon rotation of the lead screw effects linear movementof the nut toward and away from the brake disk stack.
 6. A brake as setforth in claim 5, wherein the ram nut is guided in the module housingfor movement toward and away from the brake disk stack.
 7. A brake asset forth in claim 6, wherein the module housing includes a guideway forguiding the ram nut, and the guideway and ram nut respectively havepolygonal cross-sections defined by plural outer side surfaces whichrotationally interfere with one another to restrain rotation of the ramnut relative to the housing.
 8. A brake as set forth in claim 1, incombination with an aircraft wheel assembly.
 9. A method for servicing abrake including a brake disk stack and a brake head to which a pluralityof actuator modules are removably mounted, each actuator moduleincluding a motive device operatively connected to a reciprocating ramfor selectively moving the reciprocating ram into and out of forcefulengagement with the brake disk stack for applying and releasing brakingforce, the method comprising the steps of identifying a brake module tobe replaced, and removing and replacing the identified brake module withanother brake module without disassembly of the brake disk stack.
 10. Amethod as set forth in claim 9, wherein the brake is part of a wheel andbrake assembly, and the removing and replacing step includes removingand replacing the identified brake module without removal of the wheelfrom the wheel and brake assembly.
 11. A wheel and brake assemblycomprising:a rotatable wheel; a brake disk stack operatively connectedto the wheel for applying and releasing braking torque on the rotatablewheel; a brake head; a plurality of actuator modules each including areciprocating ram, a motive device operatively connected to thereciprocating ram for selectively moving the reciprocating ram into andout of forceful engagement with the brake disk stack for applying andreleasing braking torque on the rotatable wheel, and a module housing inwhich the ram and motive device are carried, whereby the actuator moduleis removable as a unit from one side of the brake head.
 12. A wheel andbrake assembly as set forth in claim 11, wherein the actuator module isremovable from the brake head without removal of the rotatable wheel.13. A wheel and brake assembly as set forth in claim 11, wherein themodule housing includes a guideway and the ram is guided by the quidewayfor linear movement, and the guideway and ram have the same polygonalcross-sectional shape cooperating to preclude rotation of the ramrelative to the module housing.
 14. A wheel and brake assembly as setforth in claim 13, wherein the outer side surfaces of the guideway andram are planar.
 15. A wheel and brake assembly as set forth in claim 13,wherein the guide way and ram each have the cross-sectional shape of aregular polygon.
 16. A wheel and brake assembly as set forth in claim11, wherein the plurality of actuator modules are circumferentiallyequally spaced around a center axis of the brake head.
 17. A wheel andbrake assembly as set forth in claim 11, wherein the brake head includesa guideway and the ram is guided by the guideway for linear movement.18. An actuator module for use in a wheel and brake assembly including arotatable wheel, a brake disk stack operatively connected to the wheelfor applying and releasing braking force on the rotatable wheel, and abrake head; said actuator module comprising a reciprocating ram, amotive device operatively connected to the reciprocating ram forselectively moving the reciprocating ram into and out of forcefulengagement with the brake disk stack for applying and releasing brakingforce on the rotatable wheel, and a module housing in which the ram andmotive device are carried and which is configured for removableattachment to the brake head, whereby the actuator module is removablyattachable as a unit to the brake head.
 19. A wheel and brake assemblyas set forth in claim 18, wherein the module housing includes a guidewayand the ram is guided by the guideway for linear movement.